Method of recognizing and evaluating foreign substances in a pneumatically conveyed fiber stream

ABSTRACT

A method of processing fiber includes the following steps: removing fiber tufts from a series of fiber bales by a tuft removing device of a bale opener traveling along the bale series; pneumatically conveying the removed fiber tufts in a duct in a direction of conveyance; detecting foreign substances by forming images of the conveyed material by an optical sensor device as the material passes through a location of the duct downstream of the bale opener as viewed in the direction of conveyance; determining the location of each fiber bale in the bale series; determining the degree of lightness, the degree of contamination or the color of the fiber tufts by an image processing device analyzing the generated images; and associating the degree of lightness, the degree of contamination or the color of the fiber tufts with the fiber bale from which the material passing through the duct location originates.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the priority of German Application Nos. 196 31930.7 filed Aug. 8, 1996 and 197 22 582.9 filed May 30, 1997, which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a method and an apparatus in a spinningpreparation (fiber cleaning) plant for recognizing and evaluatingforeign substances, such as fabric fragments, bands, strings, foil orother thin material and the like in a pneumatically conveyed fiber whichhas been removed by a bale opener from fiber bales. The apparatusincludes an optical sensor device which recognizes foreign substancesand which is connected to an electronic control and regulating device.

According to a known method foreign substance recognition is effectedsubsequent to a preliminary (coarse) cleaning or after a mixing step,that is, prior to a fine cleaning. The fiber tufts are admitted via asuction condenser to a delivery chute, one wall of which is formed by anendlessly circulating, obliquely oriented conveyor belt. Thereafter, thefiber tufts are moved by the belt to an optical recognition system. Anevaluating device processes the measurements and if foreign substancesare detected, the appropriate sectors of a nozzle bank are activated.The nozzles of a section are actuated as soon as the upstream-arrangedoptical sensor device has recognized the foreign substances. The blastemanating from the nozzles blows the fiber tufts--with which the foreignsubstances are commingled--into a collecting bin. The other,non-contaminated good-fibers are admitted into a collecting funnel andare advanced therefrom to a subsequent cleaning machine. It is adisadvantage of such a conventional arrangement that the conveyingdevice requires a substantial technical and constructional outlay. It isa further drawback that in the known method the optical sensor deviceoperates only separately so that it cannot affect other devices andmachines of the fiber cleaning line.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved method and anapparatus of the above-outlined type from which the discusseddisadvantages are eliminated and which, in particular, makes possible ina simple manner an improved recognition and evaluation of foreignsubstances and/or colors.

This object and others to become apparent as the specificationprogresses, are accomplished by the invention, according to which,briefly stated, the method of processing fiber includes the followingsteps: removing fiber tufts from a series of fiber bales by a tuftremoving device of a bale opener traveling along the bale series;pneumatically conveying the removed fiber tufts in a duct in a directionof conveyance; detecting foreign substances by forming images of theconveyed material by an optical sensor device as the material passesthrough a location of the duct downstream of the bale opener as viewedin the direction of conveyance; determining the location of each fiberbale in the bale series; determining the degree of lightness, the degreeof contamination or the color of the fiber tufts by an image processingdevice analyzing the generated images; and associating the degree oflightness, the degree of contamination or the color of the fiber tuftswith the fiber bale from which the material passing through the ductlocation originates.

The measures according to the invention make possible to obtain dataconcerning the quality (for example, the degree of contamination) andcolor of the individual fiber bales to be opened by the bale opener. Thefiber tufts to be removed are situated almost exclusively in the insideof the standing fiber bales. By associating the values obtained by theimage processing with the individual fiber bales, such individual baleswith impermissible deviations concerning degree of contamination and/orcolor may be securely spotted and replaced if necessary. In this manner,the risks of fabric defects, for example, streaking or non-uniformcoloring are significantly reduced. Further, the invention makes itadvantageously possible to provide a new bale series with an improvedfiber mixture.

Impermissible deviations in the lightness and/or color of the fibermaterial may be detected, and also, individual light or dark fiber balesmay be spotted and, if necessary, removed. Also, erroneously set balesmay be discovered. The measuring values may also be used for thesubsequent control of after-connected processing machines such as afiber mixer. This may be effected, for example, by switching chutes inthe multi-chamber mixer. Further, predictions concerning the lightnessof the later-produced yarn may be made. The method may also be used inconnection with a continuously operating bale opener, such as a BDT 020model manufactured by Trutzschler GmbH & Co. KG, Monchengladbach,Germany, for the automatic control of the bale series as concerns thelightness fluctuations.

The invention has the further additional advantageous features:

For determining the location of each fiber bale, the travelling path ofthe fiber tuft removing device of the bale opener along the fiber balesis measured.

The detected measuring signals generated by the image processing deviceare evaluated in a signal analyzing system.

The detected measuring signals of the image processing device areinputted in a memory.

The measuring signals of the image processing device are compared withthe pre-programmed desired values.

Upon deviation from a predetermined desired value concerning a fiberbale or fiber bales, the latter are removed from the fiber bale series.

The detected measuring signals of the image processing device areutilized for composing the mixture for a fiber bale series.

Impermissible deviations from the predetermined quality values of thelightness and/or color of the fiber material of the fiber bales aredetermined.

Individual light or dark fiber bales of the fiber bale series arespotted and, if required, removed.

Erroneously set fiber bales of the fiber bale series are spotted.

The measuring values are used for controlling at least oneafter-connected machine, such as a mixer.

The measuring values serve for determining the lightness of the yarn tobe produced.

The measuring values are used in a continuously operating bale openerfor the automatic control of the bale series, for example, relative tolightness fluctuations.

The apparatus according to the invention is, in one preferredembodiment, incorporated in a fiber processing line which includes abale opener having a fiber tuft removing device for traveling along afiber bale series to remove fiber tufts from the fiber bales; a duct forguiding therein the removed fiber material as a material stream in aconveying direction; and the apparatus for recognizing and evaluatingforeign substances in the material stream guided in the duct. Theapparatus includes an electronic control and regulating device; alocation determining device, connected to the electronic control andregulating device, for determining the location of each fiber bale inthe bale series; an optical sensor device for forming images of thematerial stream at a location of the duct; and an image processingdevice connected to the electronic control and regulating device andsaid optical sensor device.

The apparatus according to the invention has the following additionaladvantageous features:

A signal analyzing device is provided for the measuring signalsgenerated by the image processing device.

A memory is provided for the measuring signals of the image processingdevice.

A comparator is provided for comparing the stored desired values and themeasuring signals of the image processing device.

At least one after-connected processing machine for example, a mixer isconnected to the electronic control and regulating device.

The upstream-connected bale opener is connected to the electroniccontrol and regulating device.

A continuously operating bale opener is coupled to the electroniccontrol and regulating device.

A switching device is connected to the electronic control and regulatingdevice.

A display device is connected to the electronic control and regulatingdevice.

A separating device is provided for the foreign substances.

The apparatus according to another preferred embodiment is incorporatedin an apparatus assembly which includes a bale opener having a fibertuft removing device for traveling along a fiber bale series to removefiber tufts from the fiber bales; a duct for guiding therein the removedfiber material as a material stream in a conveying direction from thebale opener; and the apparatus for recognizing and evaluating foreignsubstances. The apparatus is disposed upstream of the area where thebale series stands, as viewed in the fiber conveying direction. Theapparatus includes a fiber tuft removing arrangement for removing fibermaterial from a fiber bale positioned upstream of the area where thebale series stand, and for generating a fiber material stream; anoptical sensor device for forming images of the material stream; and animage processing device for processing signals generated by the opticalsensor device.

Expediently, the image processing device determines the degree oflightness and/or the degree of contamination and/or the color of thefiber material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side elevational view of a fiber processing(opening, cleaning and carding) line incorporating the apparatusaccording to the invention.

FIG. 2 is a schematic sectional side elevational view of the apparatusaccording to the invention, including an optical sensor device havingtwo cameras and four illuminating devices for picture taking intransmitted and reflected light, an image processing device and anelectronic control and regulating device.

FIG. 3 is a diagram illustrating the use of reflected light as afunction of the transmitted light for various fiber materials during thelearning phase.

FIG. 4 is a diagram illustrating the function according to FIG. 3 withfixed separation sensitivity.

FIG. 5 is a diagram illustrating the function according to FIG. 4 withrespect to various foreign substances.

FIG. 6a is a schematic side elevational view of a row of fiber bales anda fiber bale opener disposed thereabove.

FIG. 6b is a diagram, associated with FIG. 6a, showing characteristicmaterial curves associated with respective bales shown in FIG. 6a.

FIG. 6c is a diagram showing separating sensitivities relating to therespective fiber bales illustrated in FIG. 6a.

FIG. 7 is a block diagram including a control device, an X-axis pathsensor and a drive motor for the bale opener.

FIG. 8 is a schematic side elevational view, with block diagram,illustrating a bale testing apparatus according to the invention,situated ahead of the fiber bale series to be opened.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a cleaning line in which an apparatus 2 forrecognizing and separating metal foreign substances and a heavy particleseparator 3 are arranged between a bale opener 1 which may be, forexample, a BLENDOMAT BDT model manufactured by Trutzschler GmbH & Co.KG, Monchengladbach, Germany and a multi-mixer 4. Downstream of themulti-mixer 4, as viewed in the direction of travel of the processedfiber a fine opener 5 is arranged which supplies fiber tufts to aplurality of card feeders 6 (only one shown) each associated with acarding machine 7 (only one shown). The bale opener 1 in which a seriesof fiber bales 1a stand, is coupled with a condenser 8 (including ascreening drum) by means of a pneumatic conduit 9. Further, the chute 10situated downstream of the condenser 8 and the other downstream-arrangedmachines are interconnected by means of pneumatic conduits. Theinventive apparatus 11 is positioned in the conduit 9, that is, it isarranged immediately downstream of the bale opener 1.

Turning to FIG. 2, there are illustrated details of the apparatus 11.The inlet of a thoroughgoing duct 12 is coupled to a portion 9a of theconduit 9 whereas the outlet of the duct 12 is coupled to a portion 9bof the conduit 9.

To the outside of the duct 12 two housings 13 and 14 are mounted inwhich respective cameras 15 and 16 as well as illuminating devices 17and 18 are disposed. Further, in the housings 13 and 14 respectivedeflecting mirrors 19 and 20 are arranged which deflect the optical axisbetween the cameras 15 and 16 and respective windows 21 and 22 providedin the wall of the duct 12 and situated within the outline of therespective housings 13 and 14. The illuminating devices 17 and 18 sendlight through the windows 21 and 22 into the inner space of the duct 12.On the side opposite the housings 13 and 14 two further housings 23 and24 are mounted on the outside of the duct 12. In the housings 23 and 24respective illuminating devices 25 and 26 are disposed which send lightthrough duct windows 27 and 28 into the space of the duct 12. Thehousings 13, 23 and the housings 14, 24 are arranged offset with respectto one another as viewed in the direction of material flow through theduct 12.

The apparatus (fiber tuft sensor) according to the invention makespossible a recognition of foreign substances in a pneumatically conveyedstream of cotton tufts. Particularly the following types of substances(foreign bodies) are detected:

Non-transparent substances such as wood, stones, metal, strings, paper,etc; substances which are set off by their color from the fiber tufts,such as soil, leaves, etc. and bright components such as film or foilparts.

For performing the measuring process the cotton tufts are conveyedthrough the cross-sectionally rectangular duct 12. As the tufts fly bythe windows 21, 27; 22, 28 provided in the duct walls 12a, 12b, they aredetected by the cameras 15 and 16. The detecting process includes theutilization of reflected light and transmitted light by means of flashillumination by the illuminating devices 17, 25; 18, 26. The evaluationis performed according to the principle of actual and desired valuecomparison. As a desired parameter, the reflected beam intensity relatedto the transmitted beam intensity is utilized. The characteristic(lightness and color) of the cotton is automatically determined by thesystem and utilized as a reference. Foreign substances having deviatingcharacteristics are recognized if the sensed dimension along thesmallest axis amounts to, for example, 5 mm. Such foreign substances maythen be separated from the tuft stream A through a gate 29.

The housing 13 (also referred to as reflected light module) includes asemiconductor flash device 17 having a high homogeneity, acommand-controlled, high-speed measuring camera 15 having a digital dataoutput (for example, as disclosed in German Offenlegungsschrift 43 13621) and a deflecting mirror 19 for reducing the overall structuralheight. The housing 23 (also referred to as a transmitted light module)includes a large-area, semiconductor flash device 25 of high intensity.The additional housings 14 and 24 (also referred to as reflected lightand, respectively, transmitted light modules) are constructedidentically to the reflected light and transmitted light modules 13 and23.

In operation, for the determination of foreign fiber, foreignsubstances, as well as lightness and/or color of the fiber material,expediently reflected light and transmitted light is utilized. Twopictures of the same object, one with transmitted light and one withreflected light are taken in a very rapid succession. Both images arecombined and evaluated jointly. The light is applied as a flash andcontrolled by the camera 15 (and 16, if present) or by their control.For the individual pictures light of different wavelengths may be usedin which case it is feasible to use a plurality of illuminating devicesfor any picture taking. For example, the reflected light module 13 mayhave more than one illuminating device which may operate at differentwavelengths and wherein the illumination may occur from differentdirections or from different sides (transmitted light and reflectedlight). Also, the various directions, sides and wavelengths may becombined with one another and different flash durations may be set.

The camera 15, the illuminating devices 17, 25 as well as a powercylinder 30 operating a separating gate 29 are coupled to an electroniccontrol and regulating device 31. The components of the modules 14 and24, if present, are also connected to the electronic control andregulating device 31.

Between the camera 15 and the electronic control and regulating device31 an electronic image processing device 32 is connected. Such a devicemay also be provided in a similar manner if the camera 16 is present. Tothe control and regulating device 31 there are further connected amonitor 33, a signal analyzing device 34, a memory 35, a comparator 36,a switching device 37 and a device 38 (see FIG. 3) for determining thelocation of each fiber bale 1' in the fiber bale series 1a, a machinecontrol 39 (for example, for the mixer 4 and/or for the bale opener 1),a setting device 40 and a limit value forming device 46.

In operation, with the aid of the digital cameras 15 and 16, picturesbased on reflected light and transmitted light of the fiber tufts aretaken and the images are evaluated in a manner now to be described. Itis assumed that the second set of modules 14, 24 is also present.

(1) During a learning phase, by taking, for example 500 exposures, thecameras 15 and 16 are trained for the material to be processed. Duringsuch a phase the separation of foreign substances is not optimized;coarse separation takes placed based on empirical data. The learningcurve concerning the material may be seen in FIG. 3. The curvecharacterizing the material illustrates the region in which positivelyno separation should take place and is shifted dependent upon thelightness characteristics of the material and also changes its shape.

The material present in the mixture may be learned in different stages:

(a) As a mean value for all fiber bales 1' wherein the learning periodmay be one pass over all fiber bales 1';

(b) As a mean value for the bales 1' of one bale group, wherein thelearning period may be, for example, one pass over a bale group;

(c) Individually for each fiber bale 1' of a bale series 1a or a balegroup; for which purpose the X coordinate of the travel of the baleopener 1 is to be inputted in the control device 31 of the apparatus 11.Further, a synchronization with the motion start of the bale opener 1should take place. For this purpose it is often expedient to move thebale opener 1 at a lower speed than during its usual operation;

(d) In one instance upon the new introduction of the bales 1';

(e) By a sliding mean value formation in several instances in steps,distributed over the removal height of the bales 1'; and

(f) If required, values of previous, identical fiber bale series 1a maybe utilized for forming the mean value or utilized for the purposes of amore rapid optimization.

After forming the material-characteristic curve, the separationsensitivity for the separating device 29, 30 is set in two zones aboutthe curve. With reference to FIG. 4, zone A represents the region ofdefinite separation, effected immediately, while zone B represents aregion of possible separation for which suitable testing algorithms areadditionally utilized as concerns shape, lightness structure, lightnessdegree, etc.

The setting of the separating sensitivity in the zone A may be effected

(a) within defined boundaries for all materials;

(b) at a fixed distance to the material curve of the respective material(according to the possibilities 1a, 2f discussed above), wherein thezone A is adapted to the respective material curve as shown in FIG. 4;

(c) with a variable distance according to classes which are typical forforeign particles as shown in FIG. 5;

(d) additionally, by an automatic and/or semi-automatic variation of theboundaries in predetermined time intervals

according to the separation frequency (excessively little or too muchseparation);

according to a comparison with the separation of other bale types orearlier bale series; and

according to the appearing problems in the subsequent process, forexample, an increase of the cutting frequencies of the foreign fiberyarn cleaner at spool machines or open end spinning machines.

(2) The separations are to be plotted according to the type of theimpurity (for example, jute or foil) and the frequency of occurrence andmay be evaluated:

(a) for a selectable period (for example, layer);

(b) for one or more fiber bale series 1a or bale groups;

(c) for determined bale types or individual bales 1' for detectingparticularly contaminated bales.

(3) The shift of the material curves in a fiber bale series 1a may alsobe utilized over the fiber tuft removal period or between various fiberbale series 1a as a measure for the lightness differences in the mixturefor the following purposes:

(a) to detect impermissible deviations in the lightness or color of thematerial (danger of streaks in the fabrics);

(b) to detect and if needed, to separate individual, excessively lightor excessively dark bales 1' (for example, to find erroneously locatedbales 1');

(c) to use these values for the intended control of the after-connectedmixer 4 (for example, chute switching in the mixer);

(d) to make predictions concerning the lightness of the yarn to beprocessed; and

(e) in the continuously operating bale opener (which may be a BDT 020model manufactured by Trutzschler GmbH & Co. KG, Monchengladbach,Germany) to automatically control the bale series 1a with respect tolightness fluctuations.

For a reliable operation of the apparatus 11, the cameras 15 and 16 mustbe situated at a sufficient distance upstream of the separating device29, 30 as viewed in the direction of fiber travel. Should this not bethe case, there are risks that the foreign substances already havepassed the separating device before the separating gate 29 is pivotedinto its separating position. Tests have shown that the period elapsingfrom the detection of a foreign substance until the gate 29 has moved toprovide access to the waste conduit 47 amounts to 0.2 sec. Thus, in caseof a velocity of 10 m/s of the fiber/air mixture in the pneumaticconveying conduit, the distance of the cameras 15 and 16 from the gate29 should be greater than 2 m. Considering an appropriate safety factorsuch a distance should preferably be 3 m. Since, particularly largerfiber tufts travel through the conduit 9 with a lesser speed than thatof the fiber/air mixture, the separating (waste) conduit 47 must alsonot be closed prematurely. Otherwise there are risks that the foreignsubstance arrives at the gate 29 at a time when the waste conduit 47 isalready closed and thus the foreign substance is further conveyed intothe conduit portion 9b. Tests have shown that in case of a fiber/airvelocity of 10 m/sec in the conveying conduit 9 and a distance of 3 mbetween the cameras 15, 16 and the gate 29, an open period of 1 sec forthe waste conduit 47 suffices to securely separate all foreignsubstances. This period may be set in the control part of the cameras 15and 16 and may be changed for different delivery speeds in conduit 9.

Two exposures are made of the same object in a rapid sequence. From thedistance of the detected object in the picture and from the delaybetween the two exposures the velocity of the object, that is, theforeign substance itself or together with the fiber tuft may bedetermined. From the velocity the time is computed which is required forthe object to reach the separating gate 29. The thus-determined periodis applied to the control device 31 and is utilized for opening the gate29 to separate the detected object. In this manner reduction of theseparated quantities (particularly good fibers) is made possible becausethe time slot during which the gate 29 remains open may be smaller.Otherwise, since the objects have different velocities in the fiber tuftstream, such a large time window would have to be set that both thefastest and the slowest substances may be separated.

First, the determination of the conveying speed v₁ of the foreignsubstance in the zone of the cameras 15 and 16 is determined:

    V.sub.1 =d/t.sub.1

wherein

v₁ =the conveying speed of the detected object

d=the distance between two pictures

t₁ =conveying period for the distance d.

Thereafter, the transport period t₂ of the object from the cameras 15,16 to the separating gate 29 is determined:

    t.sub.2 =e/v.sub.1

wherein

t₂ =conveying period through the distance e

e=the distance between the second picture and the separating gate 29

v₁ =the conveying speed of the detected object.

The period t₂ computed in the above manner is utilized for energizingand de-energizing the pneumatic cylinder 30 for operating the separatinggate 29.

The location of each fiber bale 1' within the fiber bale series 1a maybe determined, for example, by means of an apparatus disclosed in GermanOffenlegungsschrift (application published without examination) 41 19888.

In FIG. 7 a control device 39 (for example, a memory-programmablecontrol) is shown to which an inputting device 41 is connected. A pathdetector 42, for example, an incremental path sensor mounted on thecarriage of the travelling bale opener 1 is electrically connected withthe control device 39 for determining the X axis of travel of the baleopener 1. Further, the control device 39 is connected, via an amplifier43 (control electronics, frequency converter) with the propelling motor44 for the carriage of the bale opener 1 travelling along the X axis.

The width of each fiber bale 1' and its sequence within a bale series 1amay be determined, for example, with a method and an apparatus disclosedin German Offenlegungsschrift 43 20 403.

In the FIG. 8 arrangement the apparatus 11 according to the invention isused for examining a fiber bale 1' which is situated ahead of a fiberbale series 1a to be opened. The arrangement includes a bale openingdevice 45 which is composed, for example, of a rapidly rotating tootheddevice (roll) similar to the bale opener 1 and the optical sensorapparatus 11 including an image processing device 32 as well as acontrol and regulating device 31 and an output device 46.

It will be understood that the above description of the presentinvention is susceptible to various modifications, changes andadaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

What is claimed is:
 1. A method of processing fiber comprising thefollowing steps:(a) removing fiber tufts from a series of fiber bales bya tuft removing device of a bale opener traveling along the bale series;(b) pneumatically conveying the removed fiber tufts in a duct in adirection of conveyance; (c) detecting foreign substances by formingimages of the conveyed material by an optical sensor device as thematerial passes through a location of the duct downstream of the baleopener as viewed in the direction of conveyance; (d) determining thelocation of each fiber bale in the bale series; (e) determining at leastone of a degree of lightness, a degree of contamination and a color ofthe fiber tufts by an image processing device analyzing the imagesgenerated in step (c); (f) associating at least one of a degree oflightness, a degree of contamination and a color of the fiber tuftsdetermined in step (e) with the fiber bale from which the materialpassing through said location originates; and (g) composing a new fiberbale series and utilizing the signals generated in step (e) in thecomposing step.
 2. The method as defined in claim 1, wherein step (d)comprises the step of determining the position of said tuft removingdevice as it travels along the fiber bale series.
 3. The method asdefined in claim 1, further comprising the step of applying signalsgenerated in step (e) to a memory.
 4. The method as defined in claim 1,further comprising the step of comparing signals generated in step (e)with stored desired values.
 5. The method as defined in claim 4, furthercomprising the step of determining whether the comparison of signalsgenerated in step (e) with the desired stored values yields an excessivecomparison value; and removing from the bale series the fiber bale withwhich the material having an excessive comparison value is associated.6. The method as defined in claim 1, further comprising the step ofdetermining excessive deviations of the conveyed material frompredetermined quality values of at least one of lighhtness and color. 7.The method as defined in claim 1, further comprising the step ofspotting, with the aid of signals generated in step (e), excessivelylight and excessively dark fiber bales of the bale series and separatingexcessively light and excessively dark fiber bales from the bale series.8. The method as defined in claim 1, further comprising the steps ofcontrolling a machine receiving material from said duct downstream ofsaid location and utilizing signals generated in step (e) in performingthe controlling step.
 9. A method of processing fiber comprising thefollowing steps:(a) removing fiber tufts from a series of fiber bales bya tuft removing device of a bale opener traveling along the bale series;(b) pneumatically conveying the removed fiber tufts in a duct in adirection of conveyance; (c) detecting foreign substances by formingimages of the conveyed material by an optical sensor device as thematerial passes through a location of the duct downstream of the baleopener as viewed in the direction of conveyance; (d) determining thelocation of each fiber bale in the bale series; (e) determining at leastone of a degree of lightness, a degree of contamination and a color ofthe fiber tufts by an image processing device analyzing the imagesgenerated in step (c); (f) associating at least one of a degree oflightness, a degree of contamination and a color of the fiber tuftsdetermined in step (e) with the fiber bale from which the materialpassing through said location originates; and (g) automaticallycontrolling the motions of the bale series in a continuously operatingbale opener as a function of lightness fluctuations determined fromsignals generated in step (e).
 10. The method as defined in claim 9,wherein step (d) comprises the step of determining the position of saidtuft removing device as it travels along the fiber bale series.
 11. Themethod as defined in claim 9, further comprising the step of applyingsignals generated in step (e) to a memory.
 12. The method as defined inclaim 9, further comprising the step of comparing signals generated instep (e) with stored desired values.
 13. The method as defined in claim12, further comprising the step of determining whether the comparison ofsignals generated in step (e) with the desired stored values yields anexcessive comparison value; and removing from the bale series the fiberbale with which the material having an excessive comparison value isassociated.
 14. The method as defined in claim 9, further comprising thesteps of composing a fiber bale series and utilizing the signalsgenerated in step (e) in the composing step.
 15. The method as definedin claim 9, further comprising the step of determining excessivedeviations of the conveyed material from predetermined quality values ofat least one of lightness and color.
 16. The method as defined in claim9, further comprising the step of spotting, with the aid of signalsgenerated in step (e), excessively light and excessively dark fiberbales of the bale series and separating excessively light andexcessively dark fiber bales from the bale series.
 17. The method asdefined in claim 9, further comprising the steps of controlling amachine receiving material from said duct downstream of said locationand utilizing signals generated in step (e) in performing thecontrolling step.